1. Field of the Invention
This invention concerns fuel-efficient vehicles, and more particularly relates to automotive vehicles powered by both an electric motor and an internal combustion engine, popularly known as “hybrid” vehicles.
2. Description of the Prior Art
Hybrid vehicles have been developed to improve the fuel efficiency of motor vehicles. They are powered by both an internal combustion engine and an electric motor energized by rechargeable storage batteries. The combined power of both power sources is used when maximal power is needed, such as for acceleration, towing heavy loads or climbing steep grades. The engine is generally used for cruising, and is usually severely down-sized to achieve fuel efficiency. The electric motor can be used alone but only for relatively short distances because of the limited power capacity of the batteries which soon become discharged and lose their power. Consequently, the electric motor is usually simply used to augment the power of the engine for some fairly short duty cycles such as to quickly accelerate the vehicle from a standing start and for passing. Performance can deteriorate for longer heavy duty cycles such as when climbing long grades or towing heavy loads when the down-sized engine may have to toil alone without assistance from the electric motor after the batteries become discharged.
Some hybrid vehicles have been modified to increase the cruising range of the electric motor by adding substantial numbers of storage batteries to the vehicle, and then by charging these batteries overnight using household electricity. Although such vehicles can travel as much as 60 miles between charges, and with little use of gasoline, the cost of the extra batteries is considerable. The batteries also have limited life expectancy, and the added weight of the batteries adversely affects the vehicle's fuel efficiency.
Examples of hybrid vehicles involving an internal combustion engine and one electric motor are found in the following U.S. Pat. Nos.
5,513,7195,788,0036,044,9226,209,6726,328,6716,668,9546,706,7896,712,1656,958,5496,995,4807,004,2737,028,796
Hybrid vehicles involving a single internal combustion engine in exemplified or suggested association with two or more electric motors are disclosed in the following U.S. Pat. Nos.
5,343,9716,717,2816,856,0356,959,2376,962,2246,965,1737,044,255
Hybrid vehicles have high initial and maintenance costs due to the need for an especially down-sized engine, batteries of high amperage capacity, and the associated specialized control components. These requirements make it difficult to apply current hybrid technology as after-market modifications for converting current standard automotive vehicles into fuel-efficient hybrid vehicles.
The present invention provides cost-effective solutions to the problems cited above.
Firstly, it enables the vehicle to cruise for long distances powered by an electric motor without the need for a substantially increased number of high-capacity batteries. Instead, the electric motor is energized by an on-board generator powered by a fuel-efficient internal combustion engine. This permits the vehicle to cruise over long distances with maximal fuel-efficiency using mainly the power from its electric motor. The weight of the added equipment need not significantly affect the fuel economy of the vehicle, and the cost should compare favorably with that of current hybrid vehicles.
Secondly, this invention achieves the desired fuel economy for long distance cruising without sacrificing the vehicle's performance, particularly in acceleration, load-bearing, towing and hill-climbing. This is done through the use of a separate auxiliary “accelerator” engine to add to the power of the electric motor whenever more power is needed. Since the accelerator engine is usually operated only for short periods of time, and is usually not operated while the vehicle is traveling over long distances at cruising speed, its size, power and fuel consumption need not substantially impact the over-all fuel efficiency of the vehicle. Hence, the operator can enjoy the comfort and confidence of having as much power as he desires under the hood and yet, with properly prudent driving technique, cruise with high fuel-efficiency over long distances.
This invention further permits great versatility in the choice of both the generator engine and accelerator engine. For example, the generator engine can be a small diesel engine, powerful enough to keep the batteries fully charged, and the accelerator engine can be a powerful gasoline engine, such as a Wankel rotary engine, for quick throttle response and lively performance.
The power train aspect of the present invention is easily adaptable for use as an add-on after-market modification of some existing motor vehicles which are thereby converted into fuel-efficient hybrid vehicles in a cost-effective manner.
It is accordingly a primary object of this invention to provide a hybrid vehicle capable of cruising for long distances using power from an electric motor without the need for high storage battery capacity.
It is an additional object of the present invention to provide a hybrid vehicle capable of cruising for long distances with maximal fuel-efficiency, without sacrifice of acceleration, hill climbing, and load-carrying capabilities.
It is another object of this invention to provide a fuel-efficient hybrid power train which can be installed into an existing automotive vehicle as an after-market add-on modification requiring minimal changes in said vehicle.
In one aspect of the present invention, a conventional non-hybrid vehicle having a regular engine with a horsepower in the range of about 100 to 350, a 12 volt battery, and a generator that is belt-driven by the vehicle's drive shaft is converted into a hybrid vehicle by the introduction of the following features:    a) an electrically actuated motor of about 50 to 120 horsepower which serves as the main source of power to maintain the vehicle at cruising speed for long distance travel,    b) a relatively small, fuel-efficient second internal combustion engine of about 50 to 120 horsepower henceforth referred to as a “generator” engine that drives said generator, and    c) control means causing said regular engine, henceforth referred to as the first or “accelerator” engine, to operate only when the vehicle requires additional power, as for acceleration, hill climbing, and carrying heavy loads.
In effect, such converted hybrid vehicle utilizes said motor as its primary source of power for cruising travel, and employs the accelerator engine simply as an auxiliary engine to be used only when additional power is needed. The ratio of the horsepower of the accelerator engine to the horsepower of the generator engine is preferably in the range of 1.5:1 to 3:1.
For ease of operation, the generator engine can be programmed to run automatically whenever the battery needs to be charged and to stop automatically when the battery is fully charged. For added fuel-efficiency, the electric motor can be configured as a motor/generator to charge the battery through regenerative braking, a technology which is well known in the art. For further ease of operation, the accelerator engine can be caused to start automatically whenever the gas pedal is depressed beyond what is needed to run the electric motor at full power, and to be automatically coupled to the output shaft of the electric motor, when its power is needed, through a suitable automatic clutch mechanism such as an overriding sprag clutch. Further savings in fuel consumption can be achieved if the accelerator engine is configured to be automatically shut down, namely deprived of fuel whenever the vehicle is being maintained at cruising speed by the electric motor alone. This may be controlled by the degree to which the gas pedal is depressed. Alternatively, start-up, shut down, engagement and disengagement of the accelerator engine may be controlled through the vehicle cruise control system in response to input signals from speed sensors and/or load sensors associated with the driving wheels.
In a further aspect of the present invention, a hybrid automotive vehicle is provided having a power train comprised of:    1) a first internal combustion “accelerator” engine,    2) speed change transmission means having an input shaft which receives power from said first engine,    3) an electric motor having sufficient power to maintain said vehicle at an acceptable cruising speed and delivering said power in a manner to controllably receive additional power from said first engine, and    4) an electrical supply system comprised of a) a second internal combustion “generator” engine of lesser power than said first engine, b) an electrical generator driven by said second engine, and c) a rechargeable storage battery interactive between said generator and motor.
In preferred embodiments, releasable coupling means are interactive between said accelerator engine and transmission means, enabling controlled automatic transfer of power to said transmission means. Suitable coupling means include free wheeling devices such as an overriding sprag clutch.
Said conveyance of power serves to accelerate said vehicle from a standing start to cruising speed by the combined power of said electric motor and said accelerator engine, and then, when the operator partially releases the gas pedal to stop the acceleration and to simply maintain the vehicle at cruising speed by using power from the electric motor alone, the fuel supply to said accelerator engine is diminished then stopped, causing said accelerator engine to slow down and stop, and as said accelerator engine slows down below the speed of said electric motor, said engine is automatically decoupled from said transmission input shaft through the function of said sprag clutch. Then, if or when the operator depresses the gas pedal again to provide more power than that produced by said electric motor, said accelerator engine is automatically restarted and speeded up to match the speed of said electric motor, causing said accelerator engine to be automatically coupled to said transmission input shaft through the action of said sprag clutch.
The aforesaid hybrid vehicle of this invention achieves four desirable results, namely:    a) It enables said electric motor, powered by said electric generator assembly, to maintain the vehicle at cruising speed with reduced fuel consumption per unit of distance traveled.    b) It enables the vehicle to accelerate quickly to cruising speed through the combined power of the electric motor and the accelerator engine.    c) It enables the power train, including said accelerator engine, to remain ready to be activated whenever increased power is needed. and    d) It enables the operator to selectively control the operation of said motor and said accelerator engine, including the automatic engagement and disengagement of said accelerator engine by simply depressing or releasing the gas pedal in the same manner as would have been required if he were operating a standard non-hybrid motor vehicle.
Said releasable coupling means may be a friction clutch such as the type used with standard manual transmissions, a fluid torque converter of the type generally used with automatic transmissions, a centrifugal clutch, electromagnetic clutch, or other suitable types of releasable coupling means.
In an alternative embodiment, the accelerator engine is coupled to the speed change transmission in the conventional manner (i.e., via a friction dry plate clutch in the case of a manual transmission, or via a fluid torque converter in the case of an automatic transmission) and the vehicle is accelerated from a standing start to cruising speed by power from the accelerator engine alone. After the vehicle reaches cruising speed, the speed change transmission is shifted to neutral and the vehicle is placed in a free-wheeling state.
The electric motor may be coupled to a pinion drive of a differential, completely bypassing the speed change transmission, using a power transfer means which may be an endless chain connected to sprockets, or spur gears, or combinations thereof. For added speed flexibility, a continuously variable torque converter may be installed between the electric motor output shaft and said power transfer means.
For clarity of illustration, details which are not relevant to the invention, such as engine mounts, electrical circuits, transmission mounts, internal parts of the speed change transmission, differential, transaxle, sprag clutch and continuously variable torque converter, etc., have been omitted from the aforesaid drawings.